Currently, inspection for damage or deterioration to structural bodies (e.g., aircraft composite structures) due to fatigue or impacts must be performed on a fixed schedule. These inspections are done to assess the integrity of the structure in question. Each inspection is time-consuming and is costly, not only in terms of time and skill needed to perform a thorough job, but also in terms of lost revenue from the structural bodies (e.g., aircraft) being out-of-service. Inspection of structural bodies is typically performed using what is referred to as “Non-Destructive Evaluation (NDE),” which requires careful location of multiple transducers (both actuating and sensing) on the structural body to provide for a fairly high energy path during transducer-to-transducer energy transfer.
In the case of aircraft, an automated on-board system may be designed to perform NDE, thereby eliminating the cost of potentially lost revenue from out-of-service aircraft, except when significant damage has actually occurred. In addition, because the damage has been located and/or characterized (e.g., determination of damage size, depth, etc.), repairs can be performed more quickly by using appropriate repair kits. Such an on-board system may include actuators and sensors in the form of transducers that are typically large, expensive, and require individual wiring. In certain applications, the additional weight of the wiring and/or the transducers may be prohibitive, especially for aircraft. Conventional wiring is also very heavy and requires a large amount of manual labor to install. In addition, the cost of a large number of transducers applied over a large area may be prohibitive. Another drawback to the use of large known transducers is that the signal-to-noise ratio for the long paths between the actuators and sensor is much lower than that of shorter paths. Long paths make it difficult to localize and determine the shape of a damage site.
To address these concerns, a lightweight scalable transducer system that allows the assessment of the integrity of a structural body in real-time or near real-time has been developed, as described in U.S. Pat. No. 8,447,530, which is expressly incorporated herein by reference. This lightweight scalable transducer system uses actuators, e.g., in the form of relatively inexpensive piezoelectric transducers (PZTs). The advent of direct write electronics and other additive manufacturing processes make the approach described in U.S. Pat. No. 8,447,530 more economically viable and brings possibilities of Active Damage Interrogation (ADI) during flight or ground operations. However, even with direct write of the transducers and electronics, this requires the part surface to be available for application of the wiring and materials and is best suited for investment in this at the time of manufacture of the structure.
Furthermore, it is desirable to maximize the sensitivity of an NDE system to damage or degradation of a structure by generating as much energy from the actuators in an NDE system as possible in order to provide a “clean” signal that will traverse all discontinuities in the structure. The use of relatively small and inexpensive PZT actuators in an NDE system may be fine up to a point, but these PZT actuators might not always generate enough energy to provide the desired signals. The relatively low energy signals may be integrated over time; however, this technique may extend the time to interrogate the structure longer than desired. In some scenarios, such as when the aircraft is on the ground, the structure may be hit with a rubber mallet in order to generate a relatively high energy signal that can then be sensed by the sensors of the NDE system. However, this technique cannot be performed in-flight, and cannot be routinely performed at inaccessible locations of the structure without disassembling the structure.
There, thus, remains a need for a relatively inexpensive, light-weight, and high energy transducer for use in an NDE system for monitoring of damage or deterioration in structures, such as aircraft structures.
Another issue that arises in the context of airplane flight is the accumulation of ice on leading edges of the wings and flight control surfaces, which may ultimately lead to loss of control or insufficient lift to keep the aircraft airborne, as well as the accumulation of ice on sensors, transducers, and probes, which may lead to erroneous data readings, and therefore, a potentially deleterious effect on the functioning of the aircraft. Electric deicing heaters, may be used to melt, and therefore prevent dangerous build up, of ice, on the critical components exposed to the external environment. However, this may take an extended period of time, causing scheduling delays in flights, especially if the ice is relatively thick.
There, thus, remains a need for a more efficient means to remove ice from aircraft.